1. Technical Field
The invention relates to an image processing system, an image compression system, an image editing system, a computer readable medium, a computer data signal, and an image processing apparatus.
2. Related Art
There is an image compression method, such as a mixed raster content (MRC) method specified in ITU-T recommendations T. 44.
This is a method for solving a problem that distortion of text or line drawing part increases when an image including the text or line drawing part is compressed by means of transform coding, such as JPEG.
In the MRC method, text or line drawing part is extracted from an input image. Moreover, color data of the extracted text or line drawing part is extracted. In addition, the text or line drawing part is removed from the input image. The text or line drawing part is coded as binary data by using a binary data compression method, such as MH, MMR, or JBIG. The color data is coded by using a multi-level image compression method, such as JPEG. In addition, a background image that remains after removing the text or line drawing part from the input image is coded by the multi-level image compression method, such as JPEG.
By performing the multi-plane compression described above, it becomes possible to keep the image quality of the text or line drawing part high even in the case of a high compression rate. FIG. 63 is a view cited from ITU-T recommendations T. 44. Foreground 631 indicates color data. Mask 632 indicates information of text and line drawing part, and Background 633 indicates a background image that remains after removing the text or light-emitting portion from an input image.
Alternatively, it is possible to set the text or line drawing part as binary data that is different for each color, without using the MRC format described above.
For example, a black text or line drawing part is extracted from an input image so as to create binary data. Further, a red-colored text or line drawing part is extracted from the input image so as to create binary data. Furthermore, multilevel image data in which the black or red-colored text or line drawing part is removed is created from the input image. Binary data created by extracting the black text or line drawing part is compressed in a binary data compression method. Moreover, information indicating black is additionally granted to a color of the image. In the same manner, binary data created by extracting the red-colored text or line drawing part is compressed in the binary data compression method. In addition, information indicating a red color is additionally granted to a color of the image. In addition, a background image that remains after removing the text or line drawing part from the input image is coded by the multi-level image compression method, such as JPEG.
As shown in FIG. 64, in the case when an input image 641 including a text (‘ABC’; red-colored text 6411) that is drawn by a red color, a text (‘DEF’; black text 6412) that is drawn by black, and a non-text line drawing part (image part where a house is drawn; house image 6413) exists, the input image 641 is divided into a binary image 642 obtained by extracting only ‘ABC’, a binary image 643 obtained by extracting only ‘DEF’, and a multilevel image 644 that is the rest parts and the binary image 642, the binary image 643, and the multilevel image 644 are independently coded. In addition, information, which indicates that a color of the binary image 642 obtained by extracting ‘ABC’ is a red color and a color of the binary image 643 obtained by extracting ‘DEF’ is black, is additionally granted.
In the case when the background image is created as described above, high-frequency components are generated if the text or line drawing part is simply removed. As a result, the created image becomes not suitable for the transform coding, such as JPEG. By compensating for the extracted text or line drawing part, the compression efficiency may be improved. A compensated pixel value is arbitrary because the compensated pixel value is overwritten in the text and line drawing part at the time of decoding. Accordingly, various kinds of compensation methods have been proposed.